MAESTRO Sun Scan Analysis Florian Nichitiu May 14, 2004

After on-orbit commissioning of the spacecraft and instruments a series of on-orbit science-oriented activities have been undertaken. Sun Scanning (Open Loop): 21 Feb High Sun Scanning (Closed Loop): 14 – 17 Apr The purpose of these activities is to: - extend and verify the results obtained during pre-launch lab-tests - to find the appropriate parameters for operational measurements. ***  MAESTRO field of view characterization, UV and VIS slit position, using Sun Scan measurements.  On-orbit dispersion equations, absolute sensitivity using High Sun measurements  Closed Loop offset sun-pointing parameters using High Sun Scan measurements

Sun Scan Sun tracker in Open Loop

S/C motion during High Sun Sun tracker on Closed Loop

High Sun spectra Sun tracker in Closed Loop

Occultation  High Sun  Occultation  Bg. (dark current)

Sun Scanning (Open Loop)

Sun Scanning (Open Loop) : sun scan in azimuth (elevation) with elevation(azimuth) fixed

Maximum of spectrum integral during Sun Scan

Hestroffer Solar Limb Darkening. model: (Atron. Astrophys 333, (1998))

UV =0.26 mrad VIS

Solar Scan in elevation 21 Feb Solar Disk dimension as expected: Solar disk radius = 4.6 mrad

Using time as parameter  Sun centroid in Imag coordinates

Slit position on the NIR imager : - Sun Scan analysis - DFL: final test

Slit position on the NIR imager and Sun position during CL

Maestro spectra vs. Solar Spectra

Dispersion eq. For calculating wavelength (nm) from pixel number: Wavelength= e-8*p^ e-6*p^ *p (From UofT Evaluation Test) Difference between smoothing and Exp. spectra. There is a shift in Wavelength ~ 3.43 nm

Data from: “Solar Flux Atlas…NSO/Kitt Peak : ftp://ftp.noao.edu/ftsftp://ftp.noao.edu/fts

UV spectra from Sun Scan 21 Feb 2004 UV spectra from High Sun 14 Apr 2005 MAESTRO spectra ‘Stability’

New dispersion equation for wavelength  Pixel (UV spectra): WL= e-8*p^ e-6*p^ *p P= *WL e-4*WL^ E-6*WL^ E-9*WL^4 ‘correction’ of UV spectra for each pixel: From counts to micro-watts per square centimeter per nanometer Data at each ~0.05 nm  averaged for ~0.3 nm ( as UV Maestro at ~ 400 nm)

L(VIS)= e-8*p^ e-6*p^ *p Correct Lambda=L(VIS)-6.08 nm P(Vis)= *L e-4*L^ e-7*L^ e-10*L^4 L(UV)= e-8*P^ e-6*P^ *P Correct Lambda=L(UV)-3.43 nm P(UV)= *L e-4*L^ e-6*L^ e9*L^4

MAESTRO VIS spectrometer absolute sensitivity Units: (counts/s)/(Wm^-2nm^-1)

MAESTRO UV spectrometer absolute sensitivity Units: (counts/s)/(Wm^-2nm^-1)

MAESTRO HIGH SUN scan 45 measurements with different sun tracker pointing positions Using Closed Loop offsets in azimuth and elevation (including the Standard CL offsets to the center of the High Sun : CL_AZ=1250; CL_EL=450)

CL_AZ=1750 CL_AZ= 750 CL_EL= -50 CL_EL=950

Spectrum integral during High Sun Scan Bg. ( spectrum integral for pointing ‘out of Sun’

Bg.   High Sun

2D fit ( polynomial second degree in CL_AZ and CL_EL)

Conclusions: From Sun Scan we find a good agreement: -For VIS and UV slit position and dimension with pre flight test. -Corrections for VIS and UV : -New dispersion equation (pixel   wave length). -New spectrometer absolute sensitivity. From High Sun Scan we confirm the appropriate Closed Loop Offsets parameters and we propose a new set of these parameters which can improve the quality of measurements. CL_AZ_offset = 1750 ( max) CL_EL_offset = 355

Acknowledgements: James Drummond Tom McElroy Denis Dufour Caroline Nowlan Kathleen Gilbert Sean D McLeod Jay Kar Jason Zou Clive Midwinter